A Nafion membrane containing a cobaltporphyrin (CoP) complex as a fixed oxygen carrier was prepared with a view to facilitate oxygen transport through the membrane. The design concept of the CoP-loaded Nafion membrane was based on the CoP's modification to place the CoP complex in a hydrophobic domain of the microphase-separated structure, in order to facilitate the oxygen transport and to maintain proton conductivity. The oxygen permeability through the CoP-loaded Nafion membrane was higher than the nitrogen permeability, and significantly enhanced at relatively-low oxygen pressures of the upstream, indicating that the fixed Col? complex acted as an oxygen hopping site to facilitate the oxygen transport. The oxygen/nitrogen permselectivity increased with the content of CoP in the Nafion membrane. Electrochemical reduction of oxygen at a glassy carbon electrode, modified with a Pt/C catalyst and the CoP-loaded Nafion membrane, provided additional support for the facilitated oxygen transport by the membrane. Increased current for the reduction of oxygen on the modified electrode by loading CoP indicated that the CoP offered the oxygen hopping site in the Nafion membrane. (c) 2008 Elsevier Ltd. All rights reserved.